"Bell" shaped sewer traps and drains are used in nearly every home and business in the United States. These traps have been used for many years as a means of preventing sewer gases from entering the building via the drainage system. The bell trap functions by holding a small amount of water in a reservoir. The drain cover extends into the water, thereby sealing off the sewer gases. If the drain is not used frequently, for example, if it is in a warm basement where the furnace is located, the water in the bell trap can evaporate quickly, thereby eliminating the seal with the bell of the drain cover and allowing sewer gases to escape up through the drain and into the house. This is very undesirable, particularly because of the unpleasant odor of sewer gases. Also, gas-tight bell traps have no provision for stopping water or other fluids from entering the building from backed-up drains. It would be desirable if a bell trap could prevent the backflow of fluids in addition to gases.
The same problems of the backflow of unpleasant fluids and gases can also occur in other types of drains and particularly pipe drains. In pipe drains there is often no trap provided for preventing the backflow of liquids and gases. It would be desirable to have a trap insert which could be retrofitted into the pipe drain to prevent the backflow of fluids and gases.
Many prior art methods have been used to prevent the backflow of liquids and gases. Such devices are shown in U.S. Pat. Nos. 3,542,057; 4,485,844; 2,348,097; 3,160,112, 3,791,401, 4,212,314, 3,173,442, 1,109,740 and 539,689. The drain plug in U.S. Pat. No. 3,542,057 uses a moveable valve member which is held closed by a spring to prevent the backflow of liquids and gases. These devices, however are cumbersome and not easily retrofitted into existing bell-shaped drains or traps. Existing retrofit devices such as that manufactured by Dranjer Corp., of Winnipeg, Manitoba, are expensive and generally need to be installed by a contractor or professional. Additionally, the Dranjer device appears to require smashing the existing drain out in order to make room for the new insert.
Accordingly, it would be desirable to have a trap insert which would enabled new or existing bell shaped traps and other types of drains to be easily and inexpensively retrofitted to eliminate the possibility of the backflow of gas and also to prevent the backflow of liquid from the sewer system.